This invention relates to an internal combustion engine comprising a compression chamber that is delimited by fixed housing walls and a movable piston mounted therein, and a porous component in which the combustion of fuel and air takes place.
From German publications DE 199 00 231 A1 and DE 197 63 407 C2, internal combustion engines that are equipped with a compression and combustion chamber that is formed by fixed housing walls and a movable piston mounted therein are known; fuel and air are fed into this chamber to allow combustion. A gas-permeable, porous component is mounted within the compression and combustion chamber, and provides the location in which the combustion of the fuel essentially takes place. The porous component in these known-in-the-art internal combustion engines is to be positioned either in a depression formed in the top of the piston or on the fixed housing walls of the compression and combustion chamber.
German Published Application 24 16 804 discloses an internal combustion piston engine, which is equipped with a chamber that is separate from the main combustion chamber. This special, separate chamber may also be positioned in a prechamber in the cylinder head. A gas-permeable structure placed in the separate chamber is designed to effect a preparation of the injected fuel, and to improve the combustion. However, the compression chamber formed by the piston and the cylinder still serves as the main combustion chamber.
In internal combustion engines in which the combustion of fuel and air takes place largely in a porous component positioned within the compression chamber or adjacent and open to this chamber, the difficulty exists that a strong inflow of heat will occur through the porous component into the compression chamber, and thus also into the fresh gas, due to large heat exchange surfaces. This results in a lower fresh gas charge, increased compression work, and a worsening of the efficiency of the internal combustion engine. Other disadvantages include increased thermal and mechanical strain on the components of the internal combustion engine in the area of the compression chamber.
One object of the invention is to produce an improved internal combustion engine of the type described above.
This object is attained pursuant to the invention. Advantageous further developments of the internal combustion engine are also described.
With the invention, an internal combustion engine including a compression chamber delimited by fixed housing walls and a movable piston arranged therein, and a porous component in which the combustion of fuel and air takes place, is provided. The porous component is arranged within a combustion chamber, which is separate from the compression chamber up to an overflow cross section for the overflow of the combustion gases from the combustion chamber into the compression chamber, whereby the overflow cross-section is substantially smaller than the cross-sectional surface of the combustion chamber. According to the invention, the combustion of the fuel that is injected into the combustion chamber takes place almost exclusively within the combustion chamber, which is filled completely by the porous component, while the compression chamber does not represent a combustion chamber at all.
One basic advantage of the internal combustion engine of the invention is that low-toxic emission combustion can be achieved. In order to prevent the disadvantageous effect of thermal inflow from the porous component, which represents a hot component, the chambers are nearly completely separated, and the size of the overflow cross-section is limited to the greatest extent possible. Thus, during gas exchange, and during compression, a basically lower heat influx into the fresh gas takes place, combined with better fresh gas charging and a higher efficiency for the internal combustion motor. Another advantage is lower thermal and mechanical strain on the internal combustion engine in the area of the compression chamber.
A preferred embodiment of the invention provides that the overflow cross-section be formed by an overflow nozzle, to which the combustion chamber tapers in the direction of the flow of combustion gas. One advantage of this embodiment is that the overflow cross-section of the overflow nozzle is small, resulting in lower thermal inflow in the direction of the compression chamber, without substantial pressure losses resulting in combustion gases flowing over from the combustion chamber into the compression chamber.
The combustion chamber is preferably circular in its cross-section, and is most preferably cylindrical in shape.
The overflow nozzle also is preferably circular in cross-section.
The combustion chamber and the overflow nozzle together preferably form a single component.
According to a particularly advantageous embodiment, the component that forms the combustion chamber and the overflow nozzle, including the porous component, is separately replaceable. This presents an advantage in terms of low maintenance costs for the internal combustion engine.
According to one preferred embodiment of the invention, a fuel injector for injecting the fuel into the combustion chamber is provided.
Preferably, the fuel can be injected directly into the porous component via an injection nozzle in the fuel injector.
According to a preferred embodiment of the invention, the injection nozzle of the fuel injector is positioned opposite the overflow cross-section or the overflow nozzle in the combustion chamber.
The fuel injector preferably projects into the combustion chamber at the end that is opposite the overflow cross-section or the overflow nozzle.
According to a preferred embodiment of the invention, the porous component is mounted within the combustion chamber via a clamping device, wherein the injection nozzle of the fuel injector projects into the combustion chamber or into the porous component through an opening in the clamping device.
According to a particularly preferred embodiment of the invention, the combustion chamber, together with the porous component and the fuel injector, forms a replaceable module. This, again, represents an advantage in terms of low maintenance costs for the internal combustion engine.
A thermally insulated layer is preferably positioned between the porous component and the inner wall of the combustion chamber.
According to a particularly preferred embodiment of the invention, the combustion chamber that houses the porous component is mounted in the cylinder head of the internal combustion engine.
Most preferably, the combustion chamber is centrally positioned, relative to the piston, within the cylinder head of the internal combustion engine.
The overflow cross-section is preferably only as large as is necessary to prevent pressure losses in the overflow of the gases to the greatest possible extent.
An embodiment of the invention will be described in greater detail on the basis of the drawing figure.